A Novel N-Staging System for Predicting Survival in Patients with Medullary Thyroid Cancer

Abstract

Background: The status of lymph node metastasis (LNM) is crucial for evaluating prognosis in patients with medullary thyroid cancer (MTC). However, only the compartment of LNM was reflected in the eighth edition (8th) of the American Joint Committee on Cancer (AJCC) N-staging system. Therefore, a more accurate N-staging system is required for MTC. Methods: Two large cohorts were included in this analysis and consisted of 1374 MTC patients from the Surveillance, Epidemiology, and End Results (SEER) database and 164 MTC patients from the Fudan University Shanghai Cancer Center (FUSCC) database. Using metastatic lymph node number (MLNN) and metastatic lymph node ratio (MLNR), a novel N-staging system that predicts the survival of MTC was derived and measured by concordance index (C-index). Results: The cutoff values were 0 and 12 for MLNN and 0.6 (MLNN≤12) and 0.75 (MLNN≥13) for MLNR. Based on the values of MLNN and MLNR, we proposed the following novel N-staging system for MTC: N0, MLNN=0; N1, 1≤MLNN≤12 and MLNR 12 and MLNR 12 and MLNR ≥0.75. Multivariate Cox analysis indicated that the novel N-staging system was an independent prognostic factor for cancerspecific survival. The C-index was higher for the novel N-staging system than for the 8th AJCC N-staging system (SEER cohort: 0.783 vs. 0.756; FUSCC cohort: 0.716 vs. 0.670). Conclusion: With some improvements, the novel N-staging system for MTC suggested from this research may be assessed for potential adoption in the next edition of the AJCC N-staging system. Funding Statement: This work was supported by National Natural Science Foundation of China (81772852), the Science and Technology Commission of Shanghai Municipality (16ZR1406600). Declaration of Interests: The authors report no conflicts of interest in this work. Ethics Approval Statement: This study was approved by the Ethics Committee of FUSCC.